Komodo dragon
Overview
The Komodo dragon also known as the Komodo monitor, is a large species of lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

 found in the Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

n islands of Komodo
Komodo (island)
Komodo is one of the 17,508 islands that make up the Republic of Indonesia. The island has a surface area of 390 km² and over 2000 inhabitants. The inhabitants of the island are descendants of former convicts who were exiled to the island and who have mixed themselves with the Bugis from...

, Rinca, Flores
Flores
Flores is one of the Lesser Sunda Islands, an island arc with an estimated area of 14,300 km² extending east from the Java island of Indonesia. The population was 1.831.000 in the 2010 census and the largest town is Maumere. Flores is Portuguese for "flowers".Flores is located east of Sumbawa...

, Gili Motang
Gili Motang
Gili Motang is a small island in Eastern Indonesia. It is part of the Lesser Sunda Islands chain, which together with the Greater Sunda Islands to the west make up the Sunda Islands.The island, volcanic in origin, is approximately 30 km² in area....

 and Gili Dasami. A member of the monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

 family (Varanidae
Varanidae
Varanidae is a group of lizards of the superfamily Varanoidea. The family is a group of carnivorous lizards which includes the largest living lizard, the Komodo dragon, and the crocodile monitor. Varanidae contains the living genus Varanus and a number of extinct taxa...

), it is the largest living species of lizard, growing to a maximum length of 3 metres (9.8 ft) in rare cases and weighing up to around 70 kilograms (154.3 lb). Their unusual size has been attributed to island gigantism
Island gigantism
Island gigantism or insular giantism is a biological phenomenon in which the size of animals isolated on an island increases dramatically in comparison to their mainland relatives....

, since there are no other carnivorous animals to fill the niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

 on the islands where they live.

However, recent research suggests that the large size of komodo dragons may be better understood as representative of a relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....

 population of very large varanid lizards that once lived across Indonesia and Australia, most of which, along with other megafauna
Megafauna
In terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...

, died out after the Pleistocene.
Encyclopedia
The Komodo dragon also known as the Komodo monitor, is a large species of lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

 found in the Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

n islands of Komodo
Komodo (island)
Komodo is one of the 17,508 islands that make up the Republic of Indonesia. The island has a surface area of 390 km² and over 2000 inhabitants. The inhabitants of the island are descendants of former convicts who were exiled to the island and who have mixed themselves with the Bugis from...

, Rinca, Flores
Flores
Flores is one of the Lesser Sunda Islands, an island arc with an estimated area of 14,300 km² extending east from the Java island of Indonesia. The population was 1.831.000 in the 2010 census and the largest town is Maumere. Flores is Portuguese for "flowers".Flores is located east of Sumbawa...

, Gili Motang
Gili Motang
Gili Motang is a small island in Eastern Indonesia. It is part of the Lesser Sunda Islands chain, which together with the Greater Sunda Islands to the west make up the Sunda Islands.The island, volcanic in origin, is approximately 30 km² in area....

 and Gili Dasami. A member of the monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

 family (Varanidae
Varanidae
Varanidae is a group of lizards of the superfamily Varanoidea. The family is a group of carnivorous lizards which includes the largest living lizard, the Komodo dragon, and the crocodile monitor. Varanidae contains the living genus Varanus and a number of extinct taxa...

), it is the largest living species of lizard, growing to a maximum length of 3 metres (9.8 ft) in rare cases and weighing up to around 70 kilograms (154.3 lb). Their unusual size has been attributed to island gigantism
Island gigantism
Island gigantism or insular giantism is a biological phenomenon in which the size of animals isolated on an island increases dramatically in comparison to their mainland relatives....

, since there are no other carnivorous animals to fill the niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

 on the islands where they live.

However, recent research suggests that the large size of komodo dragons may be better understood as representative of a relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....

 population of very large varanid lizards that once lived across Indonesia and Australia, most of which, along with other megafauna
Megafauna
In terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...

, died out after the Pleistocene. Fossils very similar to V. komodoensis have been found in Australia dating to greater than 3.8 million years ago, and its body size remained stable on Flores
Flores
Flores is one of the Lesser Sunda Islands, an island arc with an estimated area of 14,300 km² extending east from the Java island of Indonesia. The population was 1.831.000 in the 2010 census and the largest town is Maumere. Flores is Portuguese for "flowers".Flores is located east of Sumbawa...

, one of the handful of Indonesian islands where it is currently found, over the last 900,000 years, "a time marked by major faunal turnovers, extinction of the island's megafauna, and the arrival of early hominids by 880 ka."

As a result of their size, these lizards dominate the ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s in which they live. Komodo dragons hunt and ambush prey including invertebrates, birds, and mammals. Their group behaviour in hunting is exceptional in the reptile world. The diet of big Komodo dragons mainly consists of deer, though they also eat considerable amounts of carrion.

Mating begins between May and August, and the eggs are laid in September. About twenty eggs are deposited in abandoned megapode nests or in a self-dug nesting hole. The eggs are incubated for seven to eight months, hatching in April, when insects are most plentiful. Young Komodo dragons are vulnerable and therefore dwell in trees, safe from predators and cannibalistic
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...

 adults. They take about eight to nine years to mature, and are estimated to live for up to 30 years.

Komodo dragons were first recorded by Western scientists in 1910. Their large size and fearsome reputation make them popular zoo exhibits. In the wild their range has contracted due to human activities and they are listed as vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...

 by the IUCN
. They are protected under Indonesian law, and a national park
National park
A national park is a reserve of natural, semi-natural, or developed land that a sovereign state declares or owns. Although individual nations designate their own national parks differently A national park is a reserve of natural, semi-natural, or developed land that a sovereign state declares or...

, Komodo National Park
Komodo National Park
The Komodo National Park is a national park in Indonesia located within the Lesser Sunda Islands in the border region between the provinces of East Nusa Tenggara and West Nusa Tenggara. The park includes the three larger islands Komodo, Padar and Rincah, and 26 smaller ones, with a total area of...

, was founded to aid protection efforts.

Etymology

The Komodo dragon is also known as the Komodo monitor or the Komodo Island monitor in scientific literature, although this is not very common. To the natives of Komodo Island
Komodo (island)
Komodo is one of the 17,508 islands that make up the Republic of Indonesia. The island has a surface area of 390 km² and over 2000 inhabitants. The inhabitants of the island are descendants of former convicts who were exiled to the island and who have mixed themselves with the Bugis from...

, it is referred to as ora, buaya darat (land crocodile) or biawak raksasa (giant monitor).

Evolutionary history

The evolutionary development of the Komodo dragon started with the Varanus genus, which originated in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

 about 40 million years ago and migrated to Australia
Australia (continent)
Australia is the world's smallest continent, comprising the mainland of Australia and proximate islands including Tasmania, New Guinea, the Aru Islands and Raja Ampat Islands...

. Around 15 million years ago, a collision between Australia and Southeast Asia allowed the varanids to move into what is now the Indonesian archipelago, extending their range as far east as the island of Timor
Timor
Timor is an island at the southern end of Maritime Southeast Asia, north of the Timor Sea. It is divided between the independent state of East Timor, and West Timor, belonging to the Indonesian province of East Nusa Tenggara. The island's surface is 30,777 square kilometres...

. The Komodo dragon was believed to have differentiated from its Australian ancestors 4 million years ago. However, recent fossil evidence from Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

 suggests that the Komodo dragon evolved in Australia before spreading to Indonesia. Dramatic lowering of sea level during the last glacial period uncovered extensive stretches of continental shelf that the Komodo dragon colonized, becoming isolated in their present island range as sea levels rose afterwards.

Description

In the wild, an adult Komodo dragon usually weighs around 70 kilograms (154.3 lb), although captive specimens often weigh more. The largest verified wild specimen was 3.13 metre long and weighed 166 kilograms (366 lb), including undigested food. The Komodo dragon has a tail as long as its body, as well as about 60 frequently replaced serrated teeth that can measure up to 2.5 centimetre (0.984251968503937 in) in length. Its saliva is frequently blood-tinged, because its teeth are almost completely covered by gingival tissue
Gingiva
The gingiva , or gums, consists of the mucosal tissue that lies over the mandible and maxilla inside the mouth.-General description:...

 that is naturally lacerated during feeding. This creates an ideal culture for the bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 that live in its mouth. It also has a long, yellow, deeply forked tongue.

Senses

The Komodo dragon does not have an acute sense of hearing, despite its visible earholes, and is only able to hear sounds between 400 and 2000 hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

. It is able to see as far away as 300 metres (984.3 ft), but because its retinas only contain cones, it is thought to have poor night vision. The Komodo dragon is able to see in color, but has poor visual discrimination of stationary objects.
The Komodo dragon
Dragon
A dragon is a legendary creature, typically with serpentine or reptilian traits, that feature in the myths of many cultures. There are two distinct cultural traditions of dragons: the European dragon, derived from European folk traditions and ultimately related to Greek and Middle Eastern...

 uses its tongue to detect, taste, and smell stimuli
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....

, as with many other reptiles, with the vomeronasal sense using the Jacobson's organ, rather than using the nostrils. With the help of a favorable wind and its habit of swinging its head from side to side as it walks, Komodo dragons may be able to detect carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...

 from 4 – away. It only has a few taste bud
Taste bud
Taste buds contain the receptors for taste. They are located around the small structures on the upper surface of the tongue, soft palate, upper esophagus and epiglottis, which are called papillae. These structures are involved in detecting the five elements of taste perception: salty, sour,...

s in the back of its throat. Its scales, some of which are reinforced with bone, have sensory plaques connected to nerves that facilitate its sense of touch. The scales around the ears, lips, chin, and soles of the feet may have three or more sensory plaques.

The Komodo dragon was formerly thought to be deaf when a study reported no agitation in wild Komodo dragons in response to whispers, raised voices, or shouts. This was disputed when London Zoological Garden employee Joan Proctor trained a captive specimen to come out to feed at the sound of her voice, even when she could not be seen.

Ecology

The Komodo dragon prefers hot and dry places, and typically lives in dry open grassland, savanna, and tropical forest at low elevations. As an ectotherm
Ectotherm
An ectotherm, from the Greek εκτός "outside" and θερμός "hot", refers to organisms that control body temperature through external means. As a result, organisms are dependent on environmental heat sources and have relatively low metabolic rates. For example, many reptiles regulate their body...

, it is most active in the day, although it exhibits some nocturnal activity. Komodo dragons are solitary, coming together only to breed and eat. They are capable of running rapidly in brief sprints up to 20 kilometres per hour (12.4 mph), diving up to 4.5 metres (15 ft), and climbing trees proficiently when young through use of their strong claws. To catch prey that is out of reach, the Komodo dragon may stand on its hind legs and use its tail as a support. As the Komodo dragon matures, its claws are used primarily as weapons, as its great size makes climbing impractical.

For shelter, the Komodo dragon digs holes that can measure from 1–3 metres (3–10 ft) wide with its powerful forelimbs and claws. Because of its large size and habit of sleeping in these burrows, it is able to conserve body heat throughout the night and minimize its basking period the morning after. The Komodo dragon hunts in the afternoon, but stays in the shade during the hottest part of the day. These special resting places, usually located on ridges with a cool sea breeze, are marked with droppings and are cleared of vegetation. They serve as a strategic location from which to ambush deer.

Diet

Komodo dragons are carnivores. Although they eat mostly carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...

, they will also ambush live prey with a stealthy approach. When suitable prey arrives near a dragon's ambush site, it will suddenly charge at the animal and go for the underside or the throat. It is able to locate its prey using its keen sense of smell, which can locate a dead or dying animal from a range of up to 9.5 kilometres (6 mi). Komodo dragons have been observed knocking down large pigs and deer with their strong tail.

Komodo dragons eat by tearing large chunks of flesh and swallowing them whole while holding the carcass down with their forelegs. For smaller prey up to the size of a goat, their loosely articulated jaws, flexible skull, and expandable stomach allow it to swallow its prey whole. The vegetable contents of the stomach and intestines are typically avoided. Copious amounts of red saliva that the Komodo dragons produce help to lubricate the food, but swallowing is still a long process (15–20 minutes to swallow a goat). A Komodo dragon may attempt to speed up the process by ramming the carcass against a tree to force it down its throat, sometimes ramming so forcefully that the tree is knocked down. To prevent itself from suffocating while swallowing, it breathes using a small tube under the tongue that connects to the lungs. After eating up to 80 percent of its body weight in one meal, it drags itself to a sunny location to speed digestion, as the food could rot and poison the dragon if left undigested for too long. Because of their slow metabolism, large dragons can survive on as little as 12 meals a year. After digestion, the Komodo dragon regurgitates a mass of horns, hair, and teeth known as the gastric pellet, which is covered in malodorous mucus. After regurgitating the gastric pellet, it rubs its face in the dirt or on bushes to get rid of the mucus, suggesting that it, like humans, does not relish the scent of its own excretions.
The largest animals eat first, while the smaller ones follow a hierarchy. The largest male asserts his dominance and the smaller males show their submission by use of body language and rumbling hisses. Dragons of equal size may resort to "wrestling". Losers usually retreat though they have been known to be killed and eaten by victors.
The Komodo dragon's diet is wide-ranging, and includes invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s, other reptiles (including smaller Komodo dragons), bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s, bird eggs, small mammals, monkeys, wild boar, goats, deer, horses, and water buffalo. Young Komodos will eat insects, eggs, gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....

s, and small mammals. Occasionally they consume human
Human
Humans are the only living species in the Homo genus...

s and human corpses, digging up bodies from shallow graves. This habit of raiding graves caused the villagers of Komodo to move their graves from sandy to clay ground and pile rocks on top of them to deter the lizards. The Komodo dragon may have evolved to feed on the extinct dwarf elephant
Dwarf elephant
Dwarf elephants are prehistoric members of the order Proboscidea, that, through the process of allopatric speciation, evolved to a fraction of the size of their immediate ancestors...

 Stegodon
Stegodon
Stegodon , is a genus of the extinct subfamily Stegodontinae of the order Proboscidea. It was assigned to the family Elephantidae , but has also been placed in Stegodontidae . Stegodonts were present from 11.6 mya to 4,100 years ago...

that once lived on Flores, according to evolutionary biologist Jared Diamond
Jared Diamond
Jared Mason Diamond is an American scientist and author whose work draws from a variety of fields. He is currently Professor of Geography and Physiology at UCLA...

.

The Komodo dragon drinks by sucking water into its mouth via buccal pumping
Buccal pumping
Buccal pumping is a method of respiration in which the animal moves the floor of the mouth in a rhythmic manner that is externally apparent.This method has several stages. These will be described for an animal starting with lungs in a deflated state: First, the glottis is closed, and the...

 (a process also used for respiration), lifting its head, and letting the water run down its throat.

Saliva

Auffenberg described the Komodo dragon as having septic pathogens in its saliva (he described the saliva as "reddish and copious"), specifically the bacteria: E. coli, Staphylococcus
Staphylococcus
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....

 sp.
, Providencia
Providencia (bacterium)
Providencia is a Gram negative, motile bacterium of the family Enterobacteriaceae. Some strains are opportunistic pathogens in humans and can cause urinary tract infections, particularly in patients with long-term indwelling urinary catheters or extensive severe burns. Other strains Providencia...

 sp.
, Proteus
Proteus (bacterium)
Proteus is a genus of Gram-negative Proteobacteria.-Clinical significance:Three species—P. vulgaris, P. mirabilis, and P. penneri—are opportunistic human pathogens. Proteus includes pathogens responsible for many human urinary tract infections. P. mirabilis causes wound and urinary...

 morgani
and P. mirabilis. He noted that while these pathogens can be found in the mouths of wild Komodo dragons, they disappear from the mouths of captive animals, due to a cleaner diet and the use of antibiotics. This was verified by taking mucous samples from the external gum surface of the upper jaw of two freshly captured individuals. Saliva samples were analyzed by researchers at the University of Texas who found 57 different strains of bacteria growing in the mouths of three wild Komodo dragons including Pasteurella multocida
Pasteurella multocida
Pasteurella multocida is a Gram-negative, non-motile coccobacillus that is penicillin-sensitive and belongs to the Pasteurellaceae family . It can cause avian cholera in birds and a zoonotic infection in humans, which typically is a result of bites or scratches from domestic pets...

. The rapid growth of these bacteria was noted by Fredeking: "Normally it takes about three days for a sample of P. multocida to cover a petri dish
Petri dish
A Petri dish is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells or small moss plants. It was named after German bacteriologist Julius Richard Petri, who invented it when working as an assistant to Robert Koch...

; ours took eight hours. We were very taken aback by how virulent these strains were". This study supported the observation that wounds inflicted by the Komodo dragon are often associated with sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...

 and subsequent infections in prey animals. How the Komodo dragon is unaffected by these virulent bacteria remains a mystery.

In late 2005, researchers at the University of Melbourne
University of Melbourne
The University of Melbourne is a public university located in Melbourne, Victoria. Founded in 1853, it is the second oldest university in Australia and the oldest in Victoria...

 speculated that the perentie
Perentie
The Perentie is the largest monitor lizard or goanna native to Australia, and fourth largest lizard on earth, after the Komodo Dragon, crocodile monitor and the water monitor...

 (Varanus giganteus), other species of monitor, and agamids may be somewhat venomous. The team believes that the immediate effects of bites from these lizards were caused by mild envenomation. Bites on human digits by a lace monitor
Lace monitor
The Lace Monitor, or Lace Goanna, Varanus varius, is a member of the monitor lizard family, Australian members of which are commonly known as goannas. It belongs to the subgenus Varanus....

 (V. varius), a Komodo dragon, and a spotted tree monitor (V. scalaris) all produced similar effects: rapid swelling, localized disruption of blood clotting, and shooting pain up to the elbow, with some symptoms lasting for several hours.

In 2009, the same researchers published further evidence demonstrating that Komodo dragons possess a venomous bite. MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...

 scans of a preserved skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

 showed the presence of two venom glands
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

 in the lower jaw. They extracted one of these glands from the head of a terminally ill specimen in the Singapore Zoological Gardens, and found that it secreted a venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...

 containing several different toxic protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s. The known functions of these proteins include inhibition of blood clotting, lowering of blood pressure, muscle paralysis, and the induction of hypothermia, leading to shock and loss of consciousness in envenomated prey. As a result of the discovery, the previous theory that bacteria were responsible for the deaths of komodo victims was disputed.

Kurt Schwenk, an evolutionary biologist at the University of Connecticut
University of Connecticut
The admission rate to the University of Connecticut is about 50% and has been steadily decreasing, with about 28,000 prospective students applying for admission to the freshman class in recent years. Approximately 40,000 prospective students tour the main campus in Storrs annually...

 finds the discovery of these glands intriguing, but considers most of the evidence for venom in the study to be "meaningless, irrelevant, incorrect or falsely misleading". Even if the lizards have venomlike proteins in their mouths, Schwenk argues, they may be using them for a different function, and he doubts that venom is necessary to explain the effect of a Komodo dragon bite, arguing that shock and blood loss are the primary factors.

Reproduction

Mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

 occurs between May and August, with the eggs laid in September. During this period, males fight over females and territory by grappling with one another upon their hind legs with the loser eventually being pinned to the ground. These males may vomit or defecate when preparing for the fight. The winner of the fight will then flick his long tongue at the female to gain information about her receptivity. Females are antagonistic and resist with their claws and teeth during the early phases of courtship. Therefore, the male must fully restrain the female during coitus to avoid being hurt. Other courtship displays include males rubbing their chins on the female, hard scratches to the back, and licking. Copulation occurs when the male inserts one of his hemipenes into the female's cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

. Komodo dragons may be monogamous and form "pair bonds", a rare behavior for lizards.

The female lays her eggs in burrows cut into the side of a hill or in the abandoned nesting mounds of the Orange-footed Scrubfowl
Orange-footed Scrubfowl
The Orange-footed Scrubfowl, Megapodius reinwardt, is a small megapode of the family Megapodiidae.This species comprises five subspecies found on many islands in Wallacea as well as southern New Guinea and northern Australia. It is a terrestrial bird the size of a domestic chicken and dark-coloured...

 (a moundbuilder or megapode), with a preference for the abandoned mounds. Clutches contain an average of 20 eggs which have an incubation period of 7–8 months. Hatching is an exhausting effort for the neonates, who break out of their eggshells with an egg tooth
Egg tooth
In some egg-laying animals, the egg tooth is a small, sharp, cranial protuberance used by offspring to break or tear through the egg's surface during hatching...

 that falls off soon after. After cutting out the hatchlings may lie in their eggshells for hours before starting to dig out of the nest. They are born quite defenseless, and many are eaten by predators.

Young Komodo dragons spend much of their first few years in trees, where they are relatively safe from predators, including cannibalistic adults, who make juvenile dragons 10% of their diet. According to David Attenborough
David Attenborough
Sir David Frederick Attenborough OM, CH, CVO, CBE, FRS, FZS, FSA is a British broadcaster and naturalist. His career as the face and voice of natural history programmes has endured for more than 50 years...

, the habit of cannibalism may be advantageous in sustaining the large size of adults, as medium-sized prey on the islands is rare. When the young must approach a kill, they roll around in fecal matter and rest in the intestines of eviscerated animals to deter these hungry adults. Komodo dragons take about three to five years to mature, and may live for up to 50 years.

Parthenogenesis

A Komodo dragon at London Zoo named Sungai laid a clutch of eggs in late 2005 after being separated from male company for more than two years. Scientists initially assumed that she had been able to store sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...

 from her earlier encounter with a male, an adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

 known as superfecundation
Superfecundation
Superfecundation is the fertilization of two or more ova from the same cycle by sperm from separate acts of sexual intercourse. The term superfecundation is derived from fecund, meaning the ability to produce offspring....

. On December 20, 2006, it was reported that Flora, a captive Komodo dragon living in the Chester Zoo
Chester Zoo
Chester Zoo is a zoological garden at Upton-by-Chester, in Cheshire, England. It was opened in 1931 by George Mottershead and his family, who used as a basis some animals reported to have come from an earlier zoo in Shavington. It is one of the UK's largest zoos at...

 in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, was the second known Komodo dragon to have laid unfertilized eggs: she laid 11 eggs, and 7 of them hatched, all of them male. Scientists at Liverpool University in England performed genetic tests on three eggs that collapsed after being moved to an incubator, and verified that Flora had never been in physical contact with a male dragon. After Flora's eggs' condition had been discovered, testing showed that Sungai's eggs were also produced without outside fertilization. On January 31, 2008, the Sedgwick County Zoo
Sedgwick County Zoo
The Sedgwick County Zoo is an AZA-accredited wildlife park and major attraction in Wichita, Kansas. Founded in 1971 with the help of the Sedgwick County Zoological Society, the zoo has quickly become recognized both nationally and internationally for its support of conservation programs and...

 in Wichita, Kansas
Wichita, Kansas
Wichita is the largest city in the U.S. state of Kansas.As of the 2010 census, the city population was 382,368. Located in south-central Kansas on the Arkansas River, Wichita is the county seat of Sedgwick County and the principal city of the Wichita metropolitan area...

 became the first zoo in the Americas to document parthenogenesis in Komodo dragons. The zoo has two adult female Komodo dragons, one of which laid about 17 eggs on May 19–20, 2007. Only two eggs were incubated and hatched due to space issues; the first hatched on January 31, 2008 while the second hatched on February 1. Both hatchlings were males.

Komodo dragons have the ZW
ZW sex-determination system
The ZW sex-determination system is a system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects , and some reptiles, including Komodo dragons...

 chromosomal sex-determination system
Sex-determination system
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual...

, as opposed to the mammalian XY system
XY sex-determination system
The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects and some plants . In this system, females have two of the same kind of sex chromosome , and are called the homogametic sex. Males have two distinct sex chromosomes , and are called...

. Male progeny prove that Flora's unfertilized eggs were haploid (n) and doubled their chromosomes later to become diploid (2n) (by being fertilized by a polar body
Polar body
A polar body is a cell structure found inside an ovum. Both animal and plant ova possess it. It is also known as a polar cell.Asymmetrical cell division leads to the production of polar bodies during oogenesis. To conserve nutrients, the majority of cytoplasm is segregated into the secondary...

, or by chromosome duplication without cell division
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...

), rather than by her laying diploid eggs by one of the meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....

 reduction-divisions in her ovaries failing. When a female Komodo dragon (with ZW sex chromosomes) reproduces in this manner, she provides her progeny with only one chromosome from each of her pairs of chromosomes, including only one of her two sex chromosomes. This single set of chromosomes is duplicated in the egg, which develops parthenogenetically. Eggs receiving a Z chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

 become ZZ (male); those receiving a W chromosome become WW and fail to develop.

It has been hypothesized that this reproductive adaptation allows a single female to enter an isolated ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

 (such as an island) and by parthenogenesis produce male offspring, thereby establishing a sexually reproducing population (via reproduction with her offspring that can result in both male and female young). Despite the advantages of such an adaptation, zoos are cautioned that parthenogenesis may be detrimental to genetic diversity.

Discovery by the Western world

Komodo dragons were first documented by Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

ans in 1910, when rumors of a "land crocodile" reached Lieutenant van Steyn van Hensbroek of the Dutch colonial administration. Widespread notoriety came after 1912, when Peter Ouwens, the director of the Zoological Museum at Bogor
Bogor
Bogor is a city on the island of Java in the West Java province of Indonesia. The city is located in the center of the Bogor Regency , 60 kilometers south of the Indonesian capital Jakarta...

, Java, published a paper on the topic after receiving a photo and a skin from the lieutenant, as well as two other specimens from a collector. Later, the Komodo dragon was the driving factor for an expedition to Komodo Island
Komodo (island)
Komodo is one of the 17,508 islands that make up the Republic of Indonesia. The island has a surface area of 390 km² and over 2000 inhabitants. The inhabitants of the island are descendants of former convicts who were exiled to the island and who have mixed themselves with the Bugis from...

 by W. Douglas Burden in 1926. After returning with 12 preserved specimens and 2 live ones, this expedition provided the inspiration for the 1933 movie King Kong
King Kong (1933 film)
King Kong is a Pre-Code 1933 fantasy monster adventure film co-directed by Merian C. Cooper and Ernest B. Schoedsack, and written by Ruth Rose and James Ashmore Creelman after a story by Cooper and Edgar Wallace. The film tells of a gigantic island-dwelling apeman creature called Kong who dies in...

. It was also Burden who coined the common name "Komodo dragon." Three of his specimens were stuffed and are still on display in the American Museum of Natural History
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...

.

Studies

The Dutch, realizing the limited number of individuals in the wild, outlawed sport hunting and heavily limited the number of individuals taken for scientific study. Collecting expeditions ground to a halt with the occurrence of World War II, not resuming until the 1950s and 1960s, when studies examined the Komodo dragon's feeding behavior, reproduction, and body temperature. At around this time, an expedition was planned in which a long-term study of the Komodo dragon would be undertaken. This task was given to the Auffenberg family, who stayed on Komodo Island for 11 months in 1969. During their stay, Walter Auffenberg
Walter Auffenberg
Walter Auffenberg was an American herpetologist who spent almost 40 years in field research, studying reptile and amphibian paleontology and the systematics and biology of numerous reptile species, including alligators and Komodo dragons.-Early life:...

 and his assistant Putra Sastrawan captured and tagged more than 50 Komodo dragons. The research from the Auffenberg expedition would prove to be enormously influential in raising Komodo dragons in captivity. Research after the Auffenberg family has shed more light on the nature of the Komodo dragon, with biologists such as Claudio Ciofi continuing to study the creatures.

Conservation

The Komodo dragon is a vulnerable species
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...

 and is found on the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...

. There are approximately 4,000 to 5,000 living Komodo dragons in the wild. Their populations are restricted to the islands of Gili Motang
Gili Motang
Gili Motang is a small island in Eastern Indonesia. It is part of the Lesser Sunda Islands chain, which together with the Greater Sunda Islands to the west make up the Sunda Islands.The island, volcanic in origin, is approximately 30 km² in area....

 (100), Gili Dasami (100), Rinca (1,300), Komodo
Komodo (island)
Komodo is one of the 17,508 islands that make up the Republic of Indonesia. The island has a surface area of 390 km² and over 2000 inhabitants. The inhabitants of the island are descendants of former convicts who were exiled to the island and who have mixed themselves with the Bugis from...

 (1,700), and Flores
Flores
Flores is one of the Lesser Sunda Islands, an island arc with an estimated area of 14,300 km² extending east from the Java island of Indonesia. The population was 1.831.000 in the 2010 census and the largest town is Maumere. Flores is Portuguese for "flowers".Flores is located east of Sumbawa...

 (perhaps 2,000). However, there are concerns that there may presently be only 350 breeding
Breeding in the wild
Breeding in the wild is the natural process of animal reproduction occurring in the natural habitat of a given species. This terminology is distinct from animal husbandry or breeding of species in captivity...

 females. To address these concerns, the Komodo National Park
Komodo National Park
The Komodo National Park is a national park in Indonesia located within the Lesser Sunda Islands in the border region between the provinces of East Nusa Tenggara and West Nusa Tenggara. The park includes the three larger islands Komodo, Padar and Rincah, and 26 smaller ones, with a total area of...

 was founded in 1980 to protect Komodo dragon populations on islands including Komodo, Rinca, and Padar. Later, the Wae Wuul and Wolo Tado Reserves were opened on Flores to aid with Komodo dragon conservation.

Komodo dragons avoid encounters with humans. Juveniles are very shy and will flee quickly into a hideout if a human comes closer than about 100 metres (328.1 ft). Older animals will also retreat from humans from a shorter distance away. If cornered, they will react aggressively by gaping their mouth, hissing, and swinging their tail. If they are disturbed further, they may start an attack and bite. Although there are anecdotes of unprovoked Komodo dragons attacking or preying on humans, most of these reports are either not reputable or caused by defensive bites. Only a very few cases are truly the result of unprovoked attacks by abnormal individuals which lost their fear towards humans.

Volcanic activity, earthquakes, loss of habitat, fire, loss of prey due to poaching, tourism, and illegal poaching of the dragons themselves have all contributed to the vulnerable status of the Komodo dragon. Under Appendix I of CITES (the Convention on International Trade in Endangered Species), commercial trade of skins or specimens is illegal.

On Padar, a former population of the Komodo Dragon became extinct, of which the last individuals were seen in 1975. It is widely assumed that the Komodo dragon died out on Padar after a strong decline of the populations of large ungulate prey, for which poaching was most likely responsible.

In captivity

Komodo dragons have long been great zoo attractions, where their size and reputation make them popular exhibits. They are, however, rare in zoos because they are susceptible to infection and parasitic disease if captured from the wild, and do not readily reproduce. In May 2009, there were 13 European, 2 African, 35 North American, 1 Singaporean, and 2 Australian institutions that kept Komodo dragons.

The first Komodo dragon was exhibited in 1934 at the Smithsonian National Zoological Park
Smithsonian National Zoological Park
The Smithsonian National Zoological Park, commonly known as the National Zoo, is one of the oldest zoos in the United States, and as part of the Smithsonian Institution, does not charge admission. Founded in 1889, its mission is to provide leadership in animal care, science, education,...

, but it lived for only two years. More attempts to exhibit Komodo dragons were made, but the lifespan of these creatures was very short, averaging five years in the National Zoological Park. Studies done by Walter Auffenberg, which were documented in his book The Behavioral Ecology of the Komodo Monitor, eventually allowed for more successful managing and reproducing of the dragons in captivity.

A variety of different behaviors have been observed from captive specimens. Most individuals are relatively tame within a short period of time, and are capable of recognizing individual humans and discriminating between more familiar keepers. Komodo dragons have also been observed to engage in play with a variety of objects, including shovels, cans, plastic rings, and shoes. This behavior does not seem to be "food-motivated predatory behavior."

Even seemingly docile dragons may become aggressive unpredictably, especially when the animal's territory is invaded by someone unfamiliar. In June 2001, a Komodo dragon seriously injured a man when he entered its enclosure at the Los Angeles Zoo
Los Angeles Zoo
The Los Angeles Zoo , is a zoo founded in 1966 and located in Los Angeles, California. The City of Los Angeles owns the entire zoo, its land and facilities, and the animals...

 after being invited in by its keeper. He was bitten on his bare foot, as the keeper had told him to take off his white shoes, which could have potentially excited the Komodo dragon. Although he escaped, he needed to have several tendons in his foot reattached surgically.

See also

  • Dragon
    Dragon
    A dragon is a legendary creature, typically with serpentine or reptilian traits, that feature in the myths of many cultures. There are two distinct cultural traditions of dragons: the European dragon, derived from European folk traditions and ultimately related to Greek and Middle Eastern...

  • Papua monitor
    Papua monitor
    Varanus salvadorii is a monitor lizard found in New Guinea. It is also known by the common names Salvadori's monitor, Crocodile monitor, Papua monitor, and Artellia. The largest monitor lizard in New Guinea, it is believed to be one of the longest lizards in the world, reaching up to . It is the...

     (Varanus salvadorii) – A monitor lizard often asserted to be the longest lizard
  • Toxicofera
    Toxicofera
    Toxicofera , is a hypothetical clade which represents about 4600 species of extant squamates It encompasses all venomous reptile species, as well as numerous related non-venomous species....

     – A hypothetical clade
    Clade
    A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

     encompassing all venomous reptiles, including the Komodo dragon
  • Varanus priscus
    Megalania
    Megalania is a giant extinct goanna or monitor lizard. It was part of a megafaunal assemblage that inhabited southern Australia during the Pleistocene, and appears to have disappeared around 40,000 years ago...

    (formerly known as Megalania prisca) – A huge extinct varanid lizard of Pleistocene
    Pleistocene
    The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

     Australia
  • Whiptail lizards
    Cnemidophorus
    Cnemidophorus is a genus of lizards which belong to the family of Teiidae, which are commonly referred to as whiptail lizards or racerunners. Note that the nomenclature for this genus has recently been re-examined by T. W. Reeder et al. in 2002...

    – Lizards widely studied for their parthenogenesis

Further reading

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